Cardiovascular disease is a major cause of morbidity and mortality. There is recent evidence that infection due to influenza may precipitate vascular events such as myocardial infarctions and strokes. There is some evidence that influenza vaccination may prevent such events but the data are inconclusive. The investigators propose a randomized controlled trial to assess whether influenza vaccination will prevent vascular illness. Adults with clinical heart failure will be randomized to inactivated influenza vaccine or saline placebo each year for three consecutive years. They will be followed over six months for a composite of cardiovascular death, non-fatal myocardial infarction, non-fatal stroke and hospitalizations for heart failure using standardized criteria. Rigorous demonstration of influenza vaccine leading to a reduction in major adverse vascular events in patients with heart failure would lead to a major change in how these patients are managed. Given the large burden of disease both in Canada and globally, the possibility to reduce cardiovascular and stroke related death is a compelling reason to conduct this trial.